Erosion well drilling method and apparatus

ABSTRACT

A method for drilling deep wells, which includes lowering a high pressure pipe with a nozzle at its bottom down the well, filling the lower half of the pipe with a fluid, pumping an ignitable gas mixture into the pipe region above the fluid, and igniting the gas to create a high pressure reservoir of gaseous combustion products that eject the fluid through the nozzle at high velocity. The nozzle is lowered during or after each fluid ejection, the gaseous combustion products are exhausted, and then additional fluid and gas are pumped into the pipe and the gas is ignited to further deepen the well.

United States Patent 1 Godfrey EROSION WELL DRILLING METHOD AND APPARATUS [75] Inventor: Charles S. Godfrey, Berkeley, Calif.

[73] Assignee: Physics International Co., San

Leandro, Calif.

[22] Filed: June 1, 1971 [2]] Appl. No.: 148,697

[52] US. Cl 175/67, 166/63, 175/69, 175/71, 299/17 [51] Int. Cl E2lb 37/00, E2lb 45/00 [58] Field of Search 175/14, 15, 2, 57, 175/67, 93, 69, 70, 422, 71; 299/17; 166/63,

[56] References Cited UNITED STATES PATENTS 4/l956 Greene l66/63 3/I964 Buck l75/67 I DETONATOQ CONTROL DQILLING FLUID btJPPL-V [111 3,744,579 [451 July 10,1973

3,589,604 6/ 197i Paul 3,620,3 l3 11/1971 Elmore 3,075,463 l/l963 Eilers et a1 166/299 Primary ExaminerRichard E. Moore Attorney-Lindenberg, Freilich and Wasserman [5 7] ABSTRACT A method for drilling deep wells, which includes lowering a high pressure pipe with a nozzle at its bottom down the well, filling the lower half of the pipe with a fluid, pumping an ignitable gas mixture into the pipe region above the fluid, and igniting the gas to create a high pressure reservoir of gaseous combustion products that eject the fluid through the nozzle at high velocity.

The nozzle is lowered during or after each fluid ejection, the gaseous combustion products are exhausted,

and then additional fluid and gas are pumped into the pipe and the gas is ignited to further deepen the well.

8 Claims, 7 Drawing Figures OXYGEN SUPPL METHANE.

Sup l-V PATENTED JUL 0 SHEHZIFZ DEN-LING FLUID CH/QQLES 5. 6ODFQ 1 DEToNAToQ 7 1 N VEN TOR.

$4 M, WW

EROSION WELL DRILLING METHOD AND APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to methods and apparatus for forming deep wells in the earth.

2. Description of the Prior Art Deep wells, such as those formed to explore or recover oil and gas, are generally produced by rotary drilling. Conventional rotary drilling is relatively slow partly because only a limited power can be transmitted to the rock. In addition, the need for expensive drilling bits and other equipment makes the process expensive.

A large number of processes have been proposed as alternate methods for drilling wells. In order for a scheme to be practical, it should permit the application of large amounts of power to the rock. Erosion drilling, by the application of a high velocity fluid stream, has been recognized as a promising drilling method even though it requires a relatively high amount of energy for the removal of a given amount of rock, because it enables the application of very large amounts of power to the rock. This method also has the advantage of using a nozzle which is merely lowered and which need not directly contact the rock, as compared to rotary methods which require rigs to rotate as well as lower the drill and which require frequent replacement of the drill bits.

While erosion drilling by the use of high velocity streams of fluid has been recognized as highly promising, it has been thought that its utilization depended upon the availability of large capacity, high pressure mechanical pumps. Such pumps would have to force fluid at an extremely high velocity through long lengths of small diameter pipes, the lengths often exceeding several thousand feet during deep well drilling. If a pumping apparatus were available which could apply extremely high pumping horsepower to the fluid, particularly if such power could be applied closer to the bottom of the well, then practical erosion well drilling could be realized and deep wells could be drilled faster and at lower cost.

OBJECTS AND SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for the erosion drilling of wells, which enables rapid drilling with a minimum of equipment.

In accordance with one embodiment of the present invention, an erosion well drilling method is provided whichcan drill at a rapid rate even at great depths, and which utilizes a minimum of equipment. The method includes positioning a long pipe with a nozzle at the bottom in the well that is to be deepened, pumping mud or other drilling fluid into the lower portion of the pipe, and pumping an ignitable gas mixture into the portion of the pipe above the column of drilling fluid. When the gas is ignited, a high pressure reservoir of gaseous combustion products is created which ejects the drilling fluid through the nozzle at high velocity, to rapidly erode the rock beneath the nozzle and thereby deepen the well. This process is repeated many times, with the nozzle being lowered each time.

In order to enable rapid cycling of the process, a shroud is provided about the upper portion of the high pressure pipe and a valve is providedat the bottom of the shroud to connect it to the inside of the pipe. Ports at this location also open to the region outside the shroud. Drilling fluid is constantly pumped down.

through the annular region between the shroud and pipe, the fluid generally then flowing out the ports and upwardly through the well in the region outside of the shroud. After each gas ignition that results in the fluid being ejected from the pipe, the valve is opened to allow the drilling fluid to flow into the lower region of the pipe. The fact that drilling fluid is available at a great depth within the well at the beginning of each cycle, reduces the amount of time required to flll the lower pipe region with the fluid. The ignitable gases can be pumped .in very rapidly from the surface of the earth.

The novel features of the invention are set forthwith particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of erosion well drilling apparatus for performing the drilling operation in accordance with the invention, the width being of a larger scale than the height;

FIG. 2 is a partial view of the apparatus of FIG. 1, showing the ejection of drilling fluid through the nozzle;

FIG. 3 is a view similar to FIG. 2, but showing the ejection of gaseous products of combustion after the ejection of all of the drilling fluid through the nozzle;

FIG. 4 is a partial view of theapparatus of FIG. 1, showing the manner in which drilling fluid is introduced into the high pressure pipe to ready the apparatus for another drilling cycle;

FIG. 5 is a partial sectional view of another well drilling apparatus, which utilizes a reaction-reducing nozzle;

FIG. 6 is a sectional view of erosion well drilling apparatus constructed in accordance with still another embodiment of the invention, which employs alternate volumes of drilling fluid and ignitable gases that are moved in a train down the well; and

FIG. 7 is a partial sectional view of erosion well drilling apparatus constructed in accordance with yet another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS rapidly erode the earth, or rock, at the bottom 16 of the well. In accordance with the present invention, power for rapidly ejecting the drilling fluid through the nozzle is obtained by filling a lower portion of the high pressure pipe with a column of the drilling fluid andbuming an ignitable material such as an ignitable, highly pressurized gas mixture in a region of the pipe above the column of drilling fluid. The process is repeated many times, with the nozzle being lowered at each cycle, so

that a very deep well can be drilled.

The high pressure pipe has a large diameter lower part 18 and a smaller diameter upper part 20 that extends up to the surface of the earth. Apparatus is provided at the well head to pump drilling fluid and ignitable gases into the high pressure pipe 10, to ignite the gases, and to exhaust the remaining products of the combustion. This apparatus includes gas pumps 22'that can provide a high pressure of ignitable gases in the pipe, a gas mixing and control valve 24 that controls the flow of ignitable gases, a methane supply 26 for supplying methane gas, and an oxygen supply 28 for supplying oxygen and/or air to be burned with the methane. An exhaust valve 30 is also coupled to the upper end of the pipe to exhaust gaseous combustion products at the end of each cycle. A detonator control 32 controls the operation of a detonating device 34 such as a spark gap type, that ignites the ignitable gases in the pipe.

Drilling fluid is supplied from a source 36 to a pump 38 that can pump it down the well. While it would be possible to pump the drilling fluid into the upper end of the high pressure pipe 10, this could lead to delays in recycling, because it is difficult to rapidly pump the required amount of drilling fluid through the long length of high pressure pipe. Instead, a shroud 40 is provided which surrounds the upper part 20 of the high pressure pipe. A valve 42 is provided at the bottom of the shroud to couple the annular area 44 between the high pressure pipe and shroud to the inside of the high pressure pipe. Drilling fluid pumped down this annular area 44 within the shroud and outside of the high pressure pipe can enter the lower part 18 of the high pressure pipe to supply it with a column of drilling fluid. The pump 38 continues to pump drilling fluid down through the shroud even at times when the valve 42 is closed. At such times, the drilling fluid flows through ports at the lower end 46 of the shroud and upwardly through the annular region 48 of the well that lies outside of the shroud. To facilitate such flow, another pump 50 is provided that pumps out drilling fluid from the well. The outlet of the pump 50 can be connected, through a strainer that prevents the passage of debris, back to the drilling fluid supply 36.

A first step of the process of the invention includes opening the valve 42 to allow drilling fluid to flow from the annular region 44 into the lower part 18 of the high pressure pipe. The valve 42 is shown opened in FIG. 4, which is accomplished by lowering the upper part 20 of the pipe, although the valve can be constructed so that only a small valve seating portion must be moved. The valve 42 is left open for a sufficient length of time to provide a column 52 of drilling fluid at the lower end of the high pressure pipe, of a predetermined length L,. When the valve 42 is closed, the gas mixing valve 24 is opened and the gas pumps 22 drive an ignitable gas mixture into the region of the high pressure pipe 10 which lies above the column of drilling fluid 52. The ignitable gas is shown as filling a portion of the lower part 18 of the high pressure pipe and the entire length of the uppper part 20 thereof. After the gas pump 22 is stopped and the mixing valve 24 is closed, the detonator control 32 energizes the detonator 34 to ignite the column of gas in the high pressure pipe. The ignition quickly travels down the pipe so that all of the gas is quickly converted to a high pressure reservoir of gaseous combustion products, that ejects the column of drilling fluid 52 through the nozzle 12.

As the column 52 of drilling fluid is ejected through the nozzle 12, as shown in FIG. 2, the resulting high velocity stream of fluid rapidly erodes rock at the bottom of the well to deepen it. The bits of debris 54 eroded from the bottom of the well are carried up through the annular region 56 along with upwardly flowing drilling fluid. If sufficient ignitable gas has been provided, then after the entire column 52 of drilling fluid has been ejected from the nozzle, a quantity of the gaseous products of combustion shown at 58 in FIG. 3, is also ejected from the nozzle. The ejected gases rapidly rise through the annular region 56 to help carry particles of debris up along the well. After debris has risen to the level of the bottom of the shroud 46, the upward flow of drilling fluid through the annular region 48 helps to further carry out the debris until it is pumped out of the well through the pump 50.

The entire high pressure pipe 10 is lowered by gravity during each ejection of drilling fluid through the nozzle, although such lowering can be performed after complete ejection of the fluid. In order to ready the apparatus for another drilling cycle, the exhaust valve 30 is opened to exhaust some of the remaining gaseous products of combustion to lower the pressure in the pipe. Then, valve 42 is opened to admit another charge of drilling fluid that forms another column 52 of drilling fluid at the bottom of the pipe. When the valve 42 is closed, another charge of ignitable gas is pumped into the pipe and ignited. These cycles are repeated many times to repeatedly deepen the well.

The lines leading from check valve 24 and pump 38 to the well head are flexible. As the entire high pressure pipe is lowered each cycle, these lines will flex. After each predetermined length, such as 30 feet, of well as been excavated, additional 30 foot sections of high pressure pipe and shroud are installed at the location 60. The high pressure pipe may have a diameter of less than a few inches while the shroud may be only several inches in diameter.

The method of this invention enables a very high power, such as on the order of 100,000 horsepower, to be applied to the rock by the high velocity drilling fluid to deepen the well by a relatively large amount at each cycle. The length of L, of drilling fluid and the length of the pressurized gas column above it can be varied in accordance with the type of earth to be drilled, the depth at which drilling is being performed, the types of ignitable gases utilized, and other factors. In order to obtain significant deepening of the well, the length of the column of drilling fluid should be at least feet long, and the length of the column of ignitable gas should also be at least 100 feet long.

The amount of ignitable gases is chosen to efficiently eject at least a large portion of the drilling fluid, that is, to eject it at a relatively high velocity. Additional ignitable gases are provided so that all of the fluid can be ejected and so that some of the gaseous products of a combustion can also be ejected. The ejected gases may. not contribute significantly to deepening of the well,

but they can provide an upward flow of gases through to provide a low cost gas source. The gas may be pumped into the high pressure pipe at a pressure such as 3,000 psi. After detonation, the pressure may increase on the order of times so that a pressure such as 45,000 psi is available to eject the drilling fluid. The process of gas ignition is simplified by igniting it near the surface of the earth and allowing the ignition to travel down the high pressure pipe. The small diameter of the upper pipe part provides a relatively small volume to minimize the amount of extra gas which is required even in a deep well, while providing a means for filling part of the e lower pipe part with ignitable gas and for carrying the ignition down the pipe. In addition, it provides a region between itself and the shroud 40 for carrying down drilling fluid.

A variety of types of drilling fluid may be utilized. Generally, a mud-like fluid is desirable, which may contain ingredients for stabilizing the walls of the bore and ingredients providing viscous properties that reduce gravitational settling of the rock cuttings as the fluid is circulated to the surface.

As drilling fluid is ejected in a downward direction through the nozzle, the reaction tends to lift the high pressure pipe 20 upwardly. For a long length of pipe, there may be sufficient pipe weight to prevent upward movement. However, means such as anchors, cables, packers or the like can be employed to assure that the pipe will be held down, particularly at shallower depths. To prevent buckling, spacer rings or spiders having large diameter wheels bearing against the well bore can be provided at positions spaced along the length of the pipe. Another alternative is to use a thrustless nozzle.

FIG. 5 illustrates a nozzle 70 which minimizes or even eliminates upwward thrust on the high pressure pipe 10, by providing outlets 72 which eject fluid with an upward directional component, that is, in a direction angled more than 90 from the direction of fluid emanating from the downwardly oriented outlet 73 of the nozzle. Some of the energy of ejected fluid emerging through the outlets 72 can be employed to enlarge the diameter of the well bore. The fluid ejected through the outlets 72 also helps to raise cuttings up through the annular area 56, so that the energy of ejected fluid through the outlets 72 is not wasted. It is desirable to provide a converging nozzle at the bottomof the pipe to increase the velocity of the ejected fluid although the open lower end of a pipe could serve as the nozzle.

FIG. 6 illustrates an erosion drilling method which utilizes alternate volumes of drilling fluid and ignitable gas that are moved down a high pressure tube 80 that extends through the well. Each volume 82 of fluid is separated from an adjacent volume 84 of ignitable gas by a rubber or soft plastic diaphragm 86. As a volume of fluid 82 reaches the nozzle 88, a pressure gate 90 is moved into the position 90A at a location near the top of the ignitable gas volume above the lowermost volume of fluid. A detonator 92 is then operated to ignite the gas at the location 82A to create a high pressure reservoir of gaseous combustion products that eject the fluid in the volume 84A downwardly through the nozzle 88. After each ignition, the pressure gate 90 is opened and the train of diaphragm-separated volumes of drilling fluid and gas are moved down the high pressure tube 80. As the lowermost volume of drilling fluid 6 approaches the nozzle 88, it expels the combustion products of the previous ignition through the nozzle 88.

At I the well head, diaphragms 86 are introduced through a lock 94. Ignitable gas is admitted through a valve 96 into the space between alternate pairs of diaphragms, while drilling fluid is admitted through another valve 98 into the spaces between diaphragms that are not occupied by gas. The scheme of FIG. 6 facilitates rapid cycling of the drilling process to achieve a rapid average drilling rate.

As previously mentioned, a variety of ignitable gas components can be utilized to provide the high pressure that exhausts drilling fluid through the nozzle. Some of such gases which can be utilized detonate, while others which deflagrate can often be used to reduce peak transient pressures. In addition to gases, liquid propellants can be employed to create a high pressure reservoir of gaseous combustion products that can drive the drilling fluid out of the nozzle. FIG. 7 illustrates erosion drilling apparatus which employs a combustion chamber 110 which is formed at the top of the high pressure pipe, the combustion chamber having a pair of inlet nozzles 112 and 114 for spraying in liquid propellants. The nozzles 112 and 114 may be connected to tanks of nitric acid and .lP-4 jet fuel to create a high volume of gaseous combustion products in the chamber. This high pressur gas travels down the high pressure pipe 116 and forces drilling fluid 118 out through a nozzle 120. Various hypergolic propellant combinations can be employed, or fuels can be utilized which combust in the presence of .a suitable catalyst. A pair of valves 122 and 124 are shown coupled to the combustion chamber to enable the exhaust of gases after an ejection cycle and to provide means for admitting additional drilling fluid. Of course, the drilling fluid can be admitted at a lower region of the well, as in the scheme illustrated in FIG. 1. The advantage sometimes obtained with liquid propellants as compared to ignitable gases, is that less energy is expended in introducing them into the high pressure pipe apparatus.

Thus, the invention provides a method for the rapid drilling of deep wells, which includes the establishing of a column of drilling fluid at the lower end portion of a high pressure pipe and the ignition of material above the column of fluid to produce a high pressure reservoir of gaseous combustion products that ejects the fluid through a nozzle at the bottom of the pipe. In many cases, a shallow well is first drilled, and the apparatus of this invention is then utilized to greatly deepen the well. The use of ignitable gases or a liquid propellant enables the ejection of a drilling fluid with a very large hydraulic power, so that rapid erosion drillingoccurs. Not only is drilling speed enhanced, but the equipment eliminates the need for expensive drilling bits and similar devices which have been required in conventional drilling utilized heretofore. I

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

What is claimed is:

l. A method for deepening a well comprising:

establishing an elongated pipe in said well;

repeatedly filling a lower region of said pipe of at least feet in length with a column of drilling fluid;

pumping ignitable gas into a region of said pipe of at least 100 feet in length above the column of fluid to fill said region with said gas after each of said operations of filling a region with drilling fluid;

igniting said ignitable gas after each of said operations of pumping ignitable gas into said pipe, to create a high pressure reservoir of gaseous products of ignition that ejects at least some of said column of drilling fluid from the lower end of said pipe;

exhausting at least some of the products of ignition after each of said operations of igniting said gas; and

repeatedly lowering said pipe into said well.

2. A method for deepening a well comprising:

positioning an elongated pipe assembly in said well, which includes an inner pipe, a shroud around an upper region of said inner pipe, a valve near the bottom of said shroud for coupling the annular region between said shroud and inner pipe to the inside of said inner pipe; and nozzle means at the lower end of said inner pipe;

opening said valve;

pumping drilling fluid down through the region between said shroud and inner pipe and through said valve into a lower region of said inner pipe;

closing said valve; and

igniting combustible material in said pipe assembly to create a high pressure of combustion products that eject at least some of said drilling fluid through said nozzle means.

3. The method described in claim 2 wherein:

said pipe assembly includes means defining an outlet near the bottom of said shroud for releasing drilling fluid to the region between the wall of the well and the outside of said shroud; and

said pumping of drilling fluid is continued at least part of the time when said valve is closed, whereby to provide an upward flow of fluid around said shroud to help carry debris up and out of the well.

4. A method for deepening a well comprising:

successively introducing separators in said well;

establishing a volume of drilling fluid and a volume of ignitable gas between alternate successive pairs of said separators;

moving said separators and said volumes of fluid and of ignitable gas down said well; and

successively igniting each volume of ignitable gas as the volume of fluid under it reaches a position near the bottom of the well, to cause ejection of the volume of fluid.

5. The method described in claim 4 including:

establishing a pipe with a nozzle at its bottom in said well; and wherein said separators are introduced and moved down through said pipe.

6. A method for forming wells in the earth comprising:

positioning an elongated pipe in a well and with a nozzle at the lower end of the pipe so that the nozzle points downwardly and the pipe extends upwardly from it;

establishing a shroud about an upper region of said pipe, to form a first annular region between said upper pipe region and said shroud, said shroud having an outer diameter smaller than an the diameter of the well region along which it extends to form a second annular region between said shroud and the wall of said well region;

establishing a column of drilling fluid in a lower region of said pipe;

igniting a propellant in a region of said pipe above said column of drilling fluid, to thereby provide a high pressure of gaseous ignition products that force said drilling fluid out of said nozzle at high speed; and

circulating a fluid down through one of said annular regions and up through the other, whereby to provide an upward fluid flow that helps to carry up debris created by drilling fluid ejected from said nozzle.

7. A method for forming wells in the earth comprising:

positioning an elongated pipe with a nozzle at its lower end, so that the nozzle points downwardly and, the pipe extends upwardly from it;

establishing a shroud about an upper region of said pipe and a valve at the lower end of said shroud that couples the annular region between said shroud and pipe to the inside of said pipes;

pumping drilling fluid down through said annular region and through said valve into a lower region of said pipe;

igniting a propellant in a region of said pipe above said column of drilling fluid, to thereby provide a high pressure of gaseous ignition products that force said drilling fluid out of said nozzle at high speed; and

opening said valve at a time after said igniting of a propellant, to establish another column of drilling fluid in said lower pipe region, closing said valve, and again igniting a propellant in a region of said pipe above said column of drilling fluid.

8. A method for forming wells in the earth comprising:

positioning an elongated pipe with a nozzle at its lower end, so that the nozzle points downwardly and the pipe extends upwardly from it;

estabishing a column of drilling fluid in-a lower region of said pipe;

pumping an ignitable gas into a region of said pipe which extends at least feet above said column of drilling fluid to establish a column of ignitable gas of at least 100 feet in length and at a pressure of a least several atmospheres; and

igniting said column of ignitable gas, whereby to provide a high pressure of gaseous ignition products that force said drilling fluid out of said nozzle at high speed.

I t i i i 

1. A method for deepening a well comprising: establishing an elongated pipe in said well; repeatedly filling a lower region of said pipe of at least 100 feet in length with a column of drilling fluid; pumping ignitable gas into a region of said pipe of at least 100 feet in length above the column of fluid to fill said region with said gas , after each of said operations of filling a region with drilling fluid; igniting said ignitable gas after each of said operations of pumping ignitable gas into said pipe, to create a high pressure reservoir of gaseous products of ignition that ejects at least some of said column of drilling fluid from the lower end of said pipe; exhausting at least some of the products of ignition after each of said operations of igniting said gas; and repeatedly lowering said pipe into said well.
 2. A method for deepening a well comprising: positioning an elongated pipe assembly in said well, which includes an inner pipe, a shroud around an upper region of said inner pipe, a valve near the bottom of said shroud for coupling the annular region between said shroud and inner pipe to the inside of said inner pipe; and nozzle means at the lower end of said inner pipe; opening said valve; pumping drilling fluid down through the region between said shroud and inner pipe and through said valve into a lower region of said inner pipe; closing said valve; and igniting combustible material in said pipe assembly to create a high pressure of combustion products that eject at least some of said drilling fluid through said nozzle means.
 3. The method described in claim 2 wherein: said pipe assembly includes means defining an outlet near the bottom of said shroud for releasing drilling fluid to the region between the wall of the well and the outside of said shroud; and said pumping of drilling fluid is continued at least part of the time when said valve is closed, whereby to provide an upward flow of fluid around said shroud to help carry debris up and out of the well.
 4. A method for deepening a well comprising: successively introducing separators in said well; establishing a volume of drilling fluid and a volume of ignitable gas between alternate successive pAirs of said separators; moving said separators and said volumes of fluid and of ignitable gas down said well; and successively igniting each volume of ignitable gas as the volume of fluid under it reaches a position near the bottom of the well, to cause ejection of the volume of fluid.
 5. The method described in claim 4 including: establishing a pipe with a nozzle at its bottom in said well; and wherein said separators are introduced and moved down through said pipe.
 6. A method for forming wells in the earth comprising: positioning an elongated pipe in a well and with a nozzle at the lower end of the pipe so that the nozzle points downwardly and the pipe extends upwardly from it; establishing a shroud about an upper region of said pipe, to form a first annular region between said upper pipe region and said shroud, said shroud having an outer diameter smaller than the diameter of the well region along which it extends to form a second annular region between said shroud and the wall of said well region; establishing a column of drilling fluid in a lower region of said pipe; igniting a propellant in a region of said pipe above said column of drilling fluid, to thereby provide a high pressure of gaseous ignition products that force said drilling fluid out of said nozzle at high speed; and circulating a fluid down through one of said annular regions and up through the other, whereby to provide an upward fluid flow that helps to carry up debris created by drilling fluid ejected from said nozzle.
 7. A method for forming wells in the earth comprising: positioning an elongated pipe with a nozzle at its lower end, so that the nozzle points downwardly and the pipe extends upwardly from it; establishing a shroud about an upper region of said pipe and a valve at the lower end of said shroud that couples the annular region between said shroud and pipe to the inside of said pipe; pumping drilling fluid down through said annular region and through said valve into a lower region of said pipe; igniting a propellant in a region of said pipe above said column of drilling fluid, to thereby provide a high pressure of gaseous ignition products that force said drilling fluid out of said nozzle at high speed; and opening said valve at a time after said igniting of a propellant, to establish another column of drilling fluid in said lower pipe region, closing said valve, and again igniting a propellant in a region of said pipe above said column of drilling fluid.
 8. A method for forming wells in the earth comprising: positioning an elongated pipe with a nozzle at its lower end, so that the nozzle points downwardly and the pipe extends upwardly from it; establishing a column of drilling fluid in a lower region of said pipe; pumping an ignitable gas into a region of said pipe which extends at least 100 feet above said column of drilling fluid to establish a column of ignitable gas of at least 100 feet in length and at a pressure of at least several atmospheres; and igniting said column of ignitable gas, whereby to provide a high pressure of gaseous ignition products that force said drilling fluid out of said nozzle at high speed. 